ENGINE WILL CRANK BUT WON'T START

My husband replaced the battery but my car will still not start. It will turn over but will not start and run. Before we bought a new battery we tried to jump it off and there was a loud " pop or bang" type sound came from the engine area. It acted like it did not want to start but finally it eventually " broke loose" and now it acts like it wants to start but something is preventing it from doing so. Could it be a timing problem or something else? I just bought this car, I have'nt even had it a month yet. Please help us.